I cannot pretend I fully understand all details, but at some point the gnu assembler (possibly starting with 2.36) on Fedora started generating ELF notes named note.gnu.property.* that somehow when linked produce an loader.elf that both readelf and QEMU report has malformed notes. The readelf reports this:
readelf -Wn build/release/loader-strippef.elf Displaying notes found in: .note Owner Data size Description GNU 0x00000020 NT_GNU_PROPERTY_TYPE_0 Properties: x86 feature used: x86, x87, MMX, XMM, FXSR, XSAVE, x86 ISA u Xen 0x00000008 NT_VERSION (version) description data: 00 10 31 40 00 00 00 00 Xen 0x00000008 NT_ARCH (architecture) description data: 00 00 31 40 00 00 00 00 Xen 0x00000008 Unknown note type: (0x00000003) description data: 00 00 00 40 00 00 00 00 Xen 0x00000008 Unknown note type: (0x00000005) description data: 78 65 6e 2d 33 2e 30 00 Xen 0x00000004 Unknown note type: (0x00000006) description data: 6f 73 76 00 ?.? 0x00000007 Unknown note type: (0x006e6558) description data: 04 00 00 00 08 00 00 readelf: build/release/loader-stripped.elf: Warning: note with invalid namesz and/or descsz found at offset 0xc0 readelf: build/release/loader-stripped.elf: Warning: type: 0x656e6567, namesize: 0x00000008, descsize: 0x006e6558, alignment: 8 QEMU on other hand fails to run OSv in the direct kernel mode like so: ./script/run.py -k qemu-system-x86_64: Error loading uncompressed kernel without PVH ELF Note qemu failed. The logic in QEMU to load kernel in direct mode relies on the ELF note XEN_ELFNOTE_PHYS32_ENTRY that specifies an address of hvm_xen_start used to jump to when booting OSv. This ELF note as well as other XEN notes are defined in assembly in arch/x64/entry-xen.S. Because something is wrong with those notes, QEMU can not boot OSv. After some research I realized that the entry-xen object file has one extra note - GNU in .note.gnu.property section: readelf -nW build/release/arch/x64/entry-xen.o Displaying notes found in: .note.xen Owner Data size Description Xen 0x00000008 NT_VERSION (version) description data: 00 10 00 00 00 00 00 00 Xen 0x00000008 NT_ARCH (architecture) description data: 00 00 00 00 00 00 00 00 Xen 0x00000008 Unknown note type: (0x00000003) description data: 00 00 00 40 00 00 00 00 Xen 0x00000008 Unknown note type: (0x00000005) description data: 78 65 6e 2d 33 2e 30 00 Xen 0x00000004 Unknown note type: (0x00000006) description data: 6f 73 76 00 Xen 0x00000004 Unknown note type: (0x00000007) description data: 3f 2e 3f 00 Xen 0x00000008 Unknown note type: (0x00000008) description data: 67 65 6e 65 72 69 63 00 Xen 0x00000016 Unknown note type: (0x0000000a) description data: 21 77 72 69 74 61 62 6c 65 5f 70 61 67 65 5f 74 61 62 6c 65 73 00 Xen 0x00000004 Unknown note type: (0x0000000b) description data: 79 65 73 00 Xen 0x00000008 Unknown note type: (0x00000012) description data: 1c 10 00 c0 ff ff ff ff Displaying notes found in: .note.gnu.property Owner Data size Description GNU 0x00000020 NT_GNU_PROPERTY_TYPE_0 Properties: x86 ISA used: , x86 feature used: x86 I have also found somebody reported similar issue - https://sourceware.org/bugzilla/show_bug.cgi?id=27753 - which can be fixed by adding DISCARD to the linker script to filter out unwanted section from the target ELF. Besides adding DISCARD rule to the linker script this patch also cleans some issue with the assembly code to add the elf notes in entry-xen.S. Signed-off-by: Waldemar Kozaczuk <jwkozac...@gmail.com> --- arch/x64/entry-xen.S | 4 +++- arch/x64/loader.ld | 5 +++++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x64/entry-xen.S b/arch/x64/entry-xen.S index 451d35e4..0146a799 100644 --- a/arch/x64/entry-xen.S +++ b/arch/x64/entry-xen.S @@ -8,6 +8,7 @@ #define elfnote(type, valtype, value) \ .pushsection .note.xen, "a", @note; \ + .align 4; \ .long 2f-1f; \ .long 3f-2f; \ .long type; \ @@ -17,7 +18,8 @@ 2: \ valtype value; \ 3: \ - .align 4 + .align 4; \ + .popsection #define elfnote_val(type, value) elfnote(type, .quad, value) #define elfnote_str(type, value) elfnote(type, .asciz, value) diff --git a/arch/x64/loader.ld b/arch/x64/loader.ld index debdbf15..65f88d5b 100644 --- a/arch/x64/loader.ld +++ b/arch/x64/loader.ld @@ -57,6 +57,11 @@ SECTIONS HIDDEN(memcpy_decode_end = .); KEEP(*(.memcpy_decode)) } :text + /* .note.gnu.property sections should be discarded */ + /DISCARD/ : { + *(.note.gnu.property) + } + .eh_frame : AT(ADDR(.eh_frame) - OSV_KERNEL_VM_SHIFT) { *(.eh_frame) KEEP(*(.eh_frame)); } : text .rodata : AT(ADDR(.rodata) - OSV_KERNEL_VM_SHIFT) { *(.rodata*) } :text .eh_frame : AT(ADDR(.eh_frame) - OSV_KERNEL_VM_SHIFT) { *(.eh_frame) KEEP(*(.eh_frame)); } :text -- 2.35.1 -- You received this message because you are subscribed to the Google Groups "OSv Development" group. To unsubscribe from this group and stop receiving emails from it, send an email to osv-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/osv-dev/20220627185626.37945-1-jwkozaczuk%40gmail.com.
